Current rectifying apparatus



Sept. 26, 1933. F, MEYER Er AL.

CURRENT RECTIFYING APPARATUS4 Filed March 28, 1929 Patented Sept. 2 6, 1933 UNITED STATES4 1,928,203 CURRENT RECTIFYING APPARATUS Friedrich Meyer and-Hans Joachim Spanner, Berlin Halensee, Germany, assignors to Electrons, Inc.,` a .corporation of Delaware Application March 28, 1929, Serial No. 350,777,

and in Germany January 27, 1927 18 Claims.

This application is a continuation in part of our application Serial No. 247,316 filed 17 January 1928 as to all matters relating to Fig. 5 therein and a continuation in part of our ap- 5 plication Serial No. 214,192 filed 19 August 1927 Patent No. 1,784,877, granted December 6,' 1930 for all matters pertaining to Figures 2, 3, 4, 4a and 4b herein.

yThis invention relates generally to the rectifying of alternating current, and more particularly to methods) and apparatus for deriving auxiliary director pulsating current potentials from a principal current rectifying system more or less independently of the output of the principal rectifying system.

This invention further relates to gas-filled discharge devices, and particularly to rectifiers operating with a space current discharge in a gasiilled container with the aid of an incandescent or heated electron emitting cathode.

A particular object of the invention is to direct and control the discharges necessary to current rectifyng actions to prevent improperly timed discharges and discharges between the wrong electrodes.

Another object is to conserve in the matter of space needed by the device, and at the same time to provide for eiiicient operation.

A further object is to provide an arrangement permitting of rectifying high potential alternating currents without resorting to widely spaced electrodes and awkward constructions of the container or tube.

In rectifying systems having a direct or pulsating current output for supply to current consuming devices, it is frequently desirable to have available auxiliary potentials accompanied by small current consumption compared to the principal output to aid in proper control of the operation of either the rectifying system or the associated current consuming devices. For example, if the current rectifying device is a discharge tube, it may be desirable to have within such tube auxiliary electrodes for the purpose of iniiuencing the space discharge, and to apply to these electrodes chosen polarities of potential of predetermined degree. Or if the rectifying system is employed in connection with a filter system to energize the platel circuits of one or more three electrode vacuum tubes of an amplifying system it Amay be desirable to have avail- -able one or more auxiliary potentials Afor application to the grid electrodes of the tubes, which potentialsare ordinarily negative in character.

Another objectof our invention is the provision of auxiliary electrodes so spaced with reference to the anodesthat auxiliary negative potentials may be derived from the operation of the tubes to be described herein for use in establishissue of Helios.

(ci. 25o-21.5)

ing grid biases of the various tubes of standard radio receivers.

A feature of the invention is the use of screens between and around electrodes and the use of auxiliary electrodes for directing, confining an'd controlling the rectifying discharges to arrive at the results desired. Another feature is the use of the relative effects of an eliminated cathode fall at an effective electron emitting cathode and the mean free path of electrons in. a gasiilling. Simple and inexpensive construction is an additional feature.

The general operating advantages of gas-filled rectifier tubes operating with the aid of heated eective electron emitting cathodes, such as for example the well-known oxide coated cathodes of Wehnelt, the German scientist, are ably pointed out by Germershausen in an article in the June and July 1920 issues of Helios, an electrotechnical publication of Leipzig, Germany. However, Germershausen and others prior to us, have failed to arrive at satisfactory simple and inexpensive constructions for such rectifying and like discharge tubes with provisions for desirable efficiency of operation, a fact readily appreciated by examining the tubes of Germershausen illustrated in Fig. 14 of page 258 of the June 1920 'Ihe tubes shown in this iigure are so-called full wave rectifiers. There is a heated electron emitting cathode in the central portion of the bulb cio-operating with two anodes in the ends of the' two arms or extensions', from the main portion of the bulb, this to get wide separation between the anodes to conne the discharges alternately between the cathode and the respective anodes, land to avoid breakdown discharges between the anodes. Obviously, such a bulb is awkward and expensive in construction. From an operating point of view it is ineicient because of the long discharge paths physically constricted in cross-sectional area.,

fand further electrically so constricted because of the collection of electrical charges on the side walls of these paths, both of which effects make the overall drop of potential between cathode and anodes high, inconsistent and uncontrollable.

These Germershausen tubes have in them the advantage pointed out by him of substantially eliminating the so-called cathode fall" or diffor easy starting with cold electrodes, so that with other conditions, such as other gases and less favorable cathode materials, the cathode fall is 5;- even higher, and under these less favorable conditions the beneficial effect of thev heated electron emitting cathode is greater. As pointed out by Germershausen, the other drop of potential components of the discharge path are small compared to the cathode fall. These other components are two in number and comprise the drop in the luminous portion of the path and the so-called anode fall, which latter is representative of the potential needed to create ionization of the particular gas used, which in the case of argon is about 12 volts. The drop in the luminous portion depends upon the length of the discharge path, its cross-sectional area, the intensity of the discharge, the nature of the gas andthe pressure of the gas. In our practice this luminous drop is of the order of a few percent of the cathode fall; that is, a few volts. In the case of the Germershausen tubes, Fig. 14 for example, the long, constricted and electrically charged paths keep this luminous drop high andinconstant because of the inconstancy of the charges on the walls with intensity ofdischarge current. The obtaining of a positive auxiliary potential in the ordinary rectfying system is a comparatively simple matter. The present practice however seems to require a negative auxiliary potential more often than a positive, and this invention includes a manner that is simpleand not involving complicated apparatus for securing in connection with well known rectifying systems negative potentials suitable for many common' purposes, even very high negative potentials.

The several features of this invention will be best understood by a discussion in connection with the figures of the accompanying drawing.

Fig. 1 shows a so-called full wave" rectifying system in which auxiliary electrodes are included within a rectifying tube by which is derived potentials which maybe used for grid bias supply in standard radio receivers. Y

Fig. 2 shows in perspective a full-.wave alternating current rectier of the gas-filled lheated electron emitting or thermionic cathode type in which provision is made for preventing undesired discharges between the anodes by, using flat anodes shielded from each other by a heated electron emitting cathodeVand having incorpo- ,l rated therein the auxiliary electrodes of our invention. l

Fig. 3 is a modification of the arrangement shown in Fig'. 2.

Fig. 4 illustrates in perspective, a full-wave rectifier in which a shield is interposed between n the anodes so as to separate the tube into a plurality or electrically independent discharge spaces with a single emitting cathode so located as to function with both anodes, and includes auxiliary shielding'and discharge control means,

and including the auxiliary electrodes of our invention. y l

Fig. 4d is an elevation in in Fig.' 4. f y

Fig. 4b is a plan view oi' the electrode arrangement shown in Fig. 4a but with the shield16 omitted'to show the relativegspacing of the cathode, the anodes and auxiliary electrodes.

Referring to Fig. 1, RT represents a`rectifying part of the tube shown discharge tube having a single niament F adapted to be heated for electron emission from a secondary windingf Si ofv 'alternating current cited for argon' are probably. the most favorableI transformer T, and two anodes A for alternate, or full wave, rectification of alternating current supplied from the two extremities of the secondary winding S of the transformer T. The transformer T is indicated as having itsprimary winding energized from an alternating current source AC. The secondary winding S is indicated as tapped at a substantially mid or neutral point O, andthe two portions shunted by the usual by-pass condensers C. The rectifier output circuit is shown to be included between the neutral point O and a neutral point on secondary vwinding Sf, terminating in positive output terminal P1 and negative output terminal P0, across which the usual potential dividing resistance R is connected, and along which is positioned` a variable tap connected to the intermediate positive terminal Pal' by-passed by condenser C3. To the terminal Polis connected a resistance R1, along which are connected variable taps for supplying potentials to the terminals Pa, Pa each of which is shunted by a condenser C2, C4 respectively. The resistance R1 is shunted by a condenser C1. The other terminal of the resistance R1 is connected to the auxiliary electrode E11 the exact positioning of which will be hereinafter described with reference to Figs. 2-4b inclusive.

This electrode Ea cooperates with one of the anodes A A', which acts as a cathode in such cooperation, to form an auxiliary rectifying system for aiding in theproduction of the auxiliary potentials. By constructing the auxiliary electrode En small compared to the anode A, the correct sense of rectification is secured, the rectified current passing through resistance R1 by Way of points P0 and O to the anode A, when this anode is acting as a cathode Aon that half of the alternating current cycle during which it is not functioning as an anode in .the principal rectifier. The desired auxiliary potentials may be 'tapped from resistance R1 to the terminals P. and P1' as shown.

The shield the rectifying tube RT, located as shown between the two anodes A, A', assures that there will be no discharge between the two of this tube as a full wave rectifier.

In this arrangement, and utilizing terminal P0 as a reference terminal, terminals Ps" and lanodes to interfere with the normal operation P1 are progressively more positive and permit vided with the usual stem 2 through which the lead-in electrode wires pass as indicated in accordance with common practice. The tube is arranged i'or full-wave rectification by having a heated electron emitting or thermionic cathode 3 and two co-operating anodes 4 and 4, the heating/ current for the cathode being supplied by way of the two conductors 9 and 10. There is a gas-filling in the tube of low pressure; for

instance argon gas at about one millimeter of mercury pressure. The anodes 4' and 4" are atandprotected relatively to one another and the cathode by the interposed cathode '3 as shown.

The proterion is due to the fact that the intercathode and its emitted cloud o1' electrons act as screening 'or eiects against break-down discharges between the anodes. A break-down discharge between the two anodes would require a condition of suflicient positive ionization in the gas path between them to gen-Y erally ionize the discharge path. For example,

considering that phase of the alternating current cycle when anode 4 is at a maximum positive potential and anode 4" is at a maximum negative potential, and the potential between the anodes is double that between either anode and the cathode, there is a discharge by general ionization between the cathode and anode 4'. At this time the strong negative potential of anode 4" is tending to draw to its neighborhood the positive ions from the eld between the cathode and anode 4', and if it is successful in drawing suilicient positive ions to its neighborhood to energize this part of the space then a general breakdown discharge 7will occur. However, for the positive ions between the cathode and anode 4' to reach the neighborhood of anode 4" it is necessary that they pass through the cloud of. electrons continuously emitted by the cathode and the cathodes field action, and are thus subject to neutralization. Therefore, if the tendency for transferring positive ions is not too strong for the electron emission ofthe particular cathode suflicient neutralization takes place to prevent a break-down discharge. Thus in such an arrangement as that of Fig. 2 .there is a limit to the amount of discharge current or rectifying action that can be had withv a given emitting cathode.

There also has to be considered the possibility of a reverse action or discharge between the cathode and the anode that is negative. In the case of Fig. 2 the cathode is the screen or shield, and the fiat anodes are located suiciently close to the cathode that each of the spacings between the cathode and the two anodes is comparable to the mean free path of the electrons in the particular gas and pressure of it used, an effect fully explained by W. Crookes as early as about 1905 as pointed out in German Patent 209,969 led November 10, 1908. By reason of employing a separation having this mean free path relation the electron flow from the negative anode to the cathode does not create positive ionization, so that there is no general ionization or break-down discharge at this part of the system.

Hereinwe have placed auxiliary electrodes Ea and En either or both of which may be connected to the resistance R1. These electrodes are represented as small spheres, although other shapes maybe used without departing from the spirit of our invention, and, having an area much smaller than the area of the anodes 4 4", the correct sense of rectification is assured, when its corresponding anode is acting as a cathode on that half of the alternating current cycle during which it is not functioning as an anode in the principal rectication scheme of the device.

Fig. 3 modifies the arrangement of Fig. 2 by locating the emitting cathode 3 above lthe anodes 4 and 4". Since in this arrangement the cathode is removed from its interposed position the anodes are moved closer together to arrive at the separation distance comparableto the mean free path relation to prevent a discharge therebetween. The same relation pointed out connection with Fig. 2 as between the cathode and the two anodes is maintained. With this arrangement it is possible with not too high currents and potentials to prevent break-down discharge between the anodes and between 'the cathode and non-active anode for the reasons 'given in connection with Fig. 2. Obviously this second arrangement produces a better exposure of the anode surfaces to the cathode for better formation of discharge paths between the cathode by way of the electron field and the alternately operating or active anodes. Herein the electrodes Ea and E.' serve similar functions as those described with reference to Fig. 2.

Figures 4, 4a and 4b are different views of the same full-wave rectifier having two anodes 4 and 4" shielded from each other by a screen 5, the emitting cathode comprising the two spiral elements 3' and 3" connected in series relation and supplied with heating current byway of leads 9 and 10, this cathode arrangement being located at the top of the screen. A further screen 5' is interposed in a straight line path between the cathode 3 3"' and anodes 4, 4' to deflect or lengthen the path'of the discharge. This arrangement thus divides the tube 1 into two general discharge sections or spaces. The screen may be either of conducting material or insulating material superflcially rendered conductive, a. f

trical charges collected thereon, and for this reason it is not necessary to extend the space-dividing screens to the walls of the tube to completely divide off the discharge spaces. The charges on the dividing screens and walls tend to prevent undesired discharges taking place by way of the spaces between internal screens and walls.

I There is also shown an auxiliary screen 6 in the space above the cathode, which may or may not be necessary depending upon the size of the space, operating voltages and currents and resulting eld actions. Its purpose is to prevent positive ions `on thev active side of the system from escaping in undesired number through this space to the inactive side. 1t acts as an auxiliary cathode. As before stated, it need not span the space entirely if used, as the charges that collect on it will co-operate with the charges that col- Ain this respect to the cloud of electrons above the lect on the getter surface of the walls of the tube conditions of potential and current it is. not necessary to connect the screens to the cathode or any other point of controlled potential, this because there is an inherent tendency for the positive ions in the operating discharge paths to neutralize the rapidly collecting negative charges on the screens originating with the operating electrodes, so that there is a natural tendency for the screens to automatically maintain -an average potential the same as the potential of the cathode without a conductive connection thereto.

sure of it, this to prevent break-down discharge between the anode of negative phase in the operating cycle as explained in connection with Fig. 2.

Auxiliary electrodes En and En' are positioned relative to the anodes 4' 4" in a manner .similar to that described with reference to Figsg2 and 3.

The operation of the device shown in Figs. 4, 4a and 4b when connected in the circuit of Fig. 1 is readily appreciated from the inherent features of it. Considering the two discharge paths from the electron emitting cathode to the anodes 4 and 4 respectively, and assuming that phase of the alternating current cycle when anode 4 is positive and anode 4 is negative, the potential ofthe cathode being midway between the anode potentials, it is apparent that the cathode drop (at least 130 volts in argon gas of about 1 millimeter mercury pressure) is veliminated from the discharge path between the cathode and positive anode 4 by reason of the electron emitting cathode, or in other words, the resistance in this path is decidedly lowered, the remaining resistance of the luminous portion and the anode drop being but small compared to the eliminated cathode drop. At the same time the cathode drop between the non-emitting shield 5 5 and anode 4 is maintained and since the anode drop is the same in both cases, there will be no discharge between anode 4' and screen 5 'so long as the drop of potential in the luminous section of the discharge path between cathode and anode does not exceed the sum of the particular cathode drop of screen .5 and the drop of, the luminous section between screen 5 and anode 4'; that is, so long as the overall operating potential of the discharge path does not exceed that potential necessary to give the required velocity to ions to eiectivelyfree electrons from screen 5 upon bombardment in such way that it can act in eiect as a cathode.

Considering the discharge path between the cathode and anode 4, temporarily required to be inactive, the screen 5, charged walls of the tube, the cathode and its electron cloud, and Screen 6 if used, serve to effectively prevent positive ions in disturbing quantity from passing from the active section to the inactive section of the tube, so that there is no break-down ionization in this inactive portion from this source. Furthermore, anode 4 is spaced from screen 5 a distance comparable to the mean free path of the electrons, and since this is also a point of strongest eld action between screen 5 and anode 4", the electrons from anode 4" concentratedly escapevto the screen without any eiective positive ionization, but merely as a pure electroncurrent o'f very small intensity. Thus, when anode 4 is sc polarized in the operation as to be a cathode with respect to cathode 3 3", the electrons are drawn off over a short mean free path of electrons and.

do not move .in the main path over a long distance under high potential to start a reverse discharge to the emitting cathode. `It is thus pos- -sible-.to operate with unusually high voltages to the reactionbetween-the anodes 4' 4 and the i'auxiliarygelectrgdes En, En as hereinbefore described.

While we have described' our invention as characterized by certain embodiments of a device it is to be understood that detail changes may be made therein without departing from the spirit of our invention as defined` in the appended claims.

Having fully described our invention, we claim:

1. A gas-nlled discharge device having an electron emitting cathode, a plurality of co-operating anodes and a conductive screen separating said anodes from each other, said cathode being located to expose its electron iield to allfofsaid anodes, said anodes being spaced from said screen distances comparable to the mean free path of the electrons in said gas-filling, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between one of said auxiliary electrodes and an adjacent anode, when no current flows between said anode and cathode.

2. A gas-filled discharge device having an electron emitting cathode, a plurality of co-operating anodes, a conductive screen separating said anodes from each other, said cathode being located to expose its electron eld to all of said anodes, a discharge deflecting screen in each of the discharge paths between said cathode and the several anodes, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between one of said auxiliary electrodes and its adjacent anode, when no current flows between its adjacent anode and cathode.

3. A gas-filled discharge device having an electron emitting cathode, a plurality of co-operating anodes, a conductive screen between said anodes dividing said tube into as many discharge sections as there are anodes, said cathode being located to expose its electron eld to all of said anodes, a conductive screen surrounding said discharge sections, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between said auxiliary electrodes and said anodes, when no current flows between said anodes andcathode.

4. A gas-lled, discharge device having an electron emitting cathode, a plurality of cooperating anodes, screening means for directing the operating discharges between said cathode and said anodes, said screening means being conductively connected to said cathode, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced 2between said auxiliary electrodes and said anodes, when no current flows between 'said anodes and cathode.

5. A gas-tilleddischarge device having an electron emitting cathode having a plurality of sections, a plurality of co-operating anodes,v a screen dividing said device into as many discharge sections as there are anodes, each discharge section having one section of said cathode principally co-operating therewith, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between said auxiliaryelectrodes and said anodes, when no currentmilows between said anodes and cathode.

8. A gas-filled discharge device including a heatable electron emitting cathode having a plurality of sections, aplurality of co-operating anodes, means for dividing .said device into as 5 many discharge sections as there are anodes each of which sections has one vof said cathode sections cooperating principally therewith, and

auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between said auxiliary electrodes and said anodes when no current ows between saidanode and cathode.

7. A gas-filled discharge device including an electron emitting cathode, a plurality of cooperating anodes,` a screen between said ariodes, said cathode being located to independently expose its electron eldto each of said anodes, auxiliary electrode means serving to confine the discharges between said cathode and the several anodes, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may vbe produced between said auxiliary electrodes and said anodes, when no current flows between said anode and cathode.

8. A gas-illled full-wave alternating current rectifier tube including an electron emitting cathode, a pair of co-operating anodes, a conductive screen interposed betweensaid anodes, said cathode being located in a space at one edge of 'said screen to expose its electron ileld to both 4of said anodes, each of said anodes being spaced from said screen a Adistance comparable to the mean free path of electrons in said gas-iilling, and auxiliary' electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes whereby a discharge may be produced between said auxiliary electrodes and said anodes, when no current ows between said anode and cathode.

9. A gas-filled full-wave alternating current rectifier tube including an electron emitting cathode, a pair of co-operating anodes, a conductive screen interposed between said anodes dividing said tube into two discharge sections, said cathode being lbcated in a space at one edge of said screen to expose its electron field to both of said anodes, said anodes being spaced from said screen a distance comparableA to the mean free path of electrons in saidgas-filling, a conductive coating on that part of the inner surface of said tube surrounding said interior structure, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation t'o said anodes whereby a discharge may be produced between said auxiliary electrodes and said anodes, when no current iiows between said anode and cathode.

"10. A gas-lled full-wave alternating current' additional screens partially obstructing the direct paths between said cathode and each of said anodes, said anodes being spaced from said rst screen va distance comparable to the mean free vpath oi electrons in said gas-illling, and auxiliary electrodes of appreciably smaller area than said an'odes in closely spaced relation to said A' anodes whereby a discharge may be produced between said auxiliary electrodes and said anodes, @when no current flows between said anodes and cathode.

11. A gas-lled rectiiler tube for alternating current including an electron emitting cathode, a co-operating anode spaced from said cathode a distance exceeding the mean free path ofthe electrons in said gas-filling t-o provide a positive ionizing gas path therebetween, a conductive element spaced from said anode a distance comparable to the mean free path of electrons in said gas-filling and'connected to said cathode, said element being positioned with respect to said anode and discharge path to be substantially noninterfering with positive ionization of the discharge path in the direction of cathode to anode, and an auxiliary electrode of appreciably smaller area than said anode in closely spaced relation to said anode whereby a discharge may be produced between said auxiliary electrode and said anode, when no current 'ows between said anode and cathode.

l2. An electric discharge tube containing a gas, a plurality of anodes, a barrier interposed between said anodes, said barrier being spaced a distance from said anodes comparable to the mean free distance of said gas, a thermionic cathode interposed between said anodes, and auxiliary electrodes of appreciably smaller area than said anodes in closely spaced relation to said anodes.

13. A gaseous rectifier tube comprising a cathode adapted to be heated, a plurality of anodes, means disposed between said anodes for preventing a gaseous discharge therebetween, and an auxiliary electrode adjacent one of said anodes and shielded by said anode with respect to a gaseous discharge between said auxiliary electrode and said cathode. 1

14. A gaseous discharge tube comprising a thermionic cathode, an anode, and an auxiliary electrode of small dimensions and area relative to those of the anode, said anode being disposed between said cathode and said auxiliary electrode. T

15. `An electric discharge tube comprising a thermionic cathode, an anode having an extensive surface exposed toA said cathode, and an auxiliary unheated electrode-of relatively small surface disposed adjacent said anode and 'shielded by the anode from the space betweenl said cathode and anode.

v16. A full-wave rectifier tube comprising a thermionic cathode, a plurality of 4anodes each having an extensive surface exposed to said cathode, and an auxiliary unheated electrode of relatrode having a relatively small surface, and an electrode having an extensive continuous surface forming a discharge preventing shield between the aforementioned electrodes and adapted to act alternately as anode to said thermionic electrode and as cathode to said small unheated electrode.

18. An alternating current rectifier comprising a discharge tube including a main discharge anode, a thermionic cathode, and an auxiliary anode small relative to the main anode and spaced therefrom, the fsaid auxiliary anode forming with the main anodean auxiliary rectifying discharge path which is independent of the main discharge path between themain cathode 'and anode during periods of inactivity of the latter as an elevment in the principal rectifying function.

FRIEDRICH MEYER. HANS JOACHIM sPANNER. 

